Ah, well. "The Pontiac" is a region of Western Quebec. "Officially" speaking the boundaries of it are one thing, what the locals say the boundaries are is something else. And I suppose "Black Hills" is a local name.

Try Googling "Waltham, Quebec," to get closer to where he was on the map. That road runs off the 148 just to the east of the village (which is so small it might not be on most maps). You're looking specifically for "Chemin de La Rivere Noir". Or, the maps might be in English, in which case "Black River Road"...

Good geography class lesson! The maps do not always reflect the territory.